Apparatus and process for heating fluids



Oct. 10, 1933. w A DARRAH 1,929,881

APPARATUS AND PROCESS FOR HEATING FLUIDS Filed March 11, 1929 2 Sheets-Sheet l [72 (7:72 tar.

Oct. 10, 1933. w. A. DARRAH 1,929,331

APPARATUS AND PROCESS FOR HEATING FLUIDS Filed March 11, 1929 2 Sheets-Sheet 2 Fig ure? 4 Rye/Fe i Patented Oct. 10, 1933 UNITED-STATES APPARATUS AND PROCESS FOR HEATING FLUIDS WilliamA. Dal-rah, Chicago, Application March' 11, 1929. Serial No. 346,228

4 Claims. (01. 2ss-20) This invention relates to equipment and methods for heating air or other gases or vapors. Among the objects of this invention are to provide economical, simple and efficient means for heating large quantities of air or other gases. This equipment also permits the maintenance of uniform temperatures, automatically if desired, and extracts a large amount of heat from the combustion gases.

This equipment is also designed to permit quick, ready and inexpensive maintenance to provide easy access for cleaning and to be free from deterioration due to oxidation or other difficulties due to high temperatures.

Further objects of this invention are to permit accurate, close and simultaneous control of temperature in the circulating air by mechanical means. Another object of this invention is to provide operating safeguards and means for avoiding damage to the equipment under various conditions encountered in operation.

R.eferring to the drawings:

Figure 1 shows a side elevation partly in section of one form of my invention.

Figure 2 shows an end elevation also partly in section, illustrating further details of the equipment and the flow of air or gases through the equipment.

Figure 3 is a .plan view showing sections through variousportions.

Figure 4 shows an outside end elevation of one form of my invention applied to a drying or heating device indicating some of the auxiliary equipment.

Figure 5 shows diagrammatically the application of mechanical control means to one form of my invention.

The equipment consists of a shell or.enc1osure 1 which may be made of brick and encased in steel or other material as desired. In the drawings, for purposes of illustration it is shownas formed with brick walls 2, provided with insulation material 3 to reduce the heat loss and enclosed in a steel shell 4.

In the lower portion of enclosure 1, is located a combustion chamber 4 in which is diagrammatically shown a stoker 5 arranged to feed fuel to the combustion chamber from a hopper 6.

It should be understood that other forms of combustion equipment may be employed and while eitherv solid, liquid or gaseous fuel may be consumed this particular description will cover equipment designed to handle solid fuel for purposes of illustration. The fuel is forced from hopper 6 through a retort 7 into grate 8.

The fuel bed is indicated diagrammatically by 9,

while 10 indicates an ash pit with ports or doors 11 throughwhich the ashes may be removed, the doors being normally closed. A bridge wall 12 is provided beyond grate 8 to limit combustion.

The products of combustion travel along the lines shown by the arrows leaving the bed of fuel above the grate passing throughdust collecting chamber 13 up fine 14 into header space 15 and through metallic fines 16. Abypass stackl'l is provided above flue 14 and equipped withav damper 18 for purposes later to be described.

After passing through 'metallic flues 16, the products of combustion accumulate in heated space 19 and then pass upward through stack 20 which is controlled by damper 21. 7

Air for combustion is drawn downward through ports 22 into preheating fines 23 and. into the intake 24 of forced draft fan 25. The solid arrows show the direction of travel-of. combustion air up to .fan 25. From fan25 the combustion air now appreciably heated passes by flue 26 as shown by the broken line arrow. intodistributing flue 27 and then upward into space 28 be'neath the grate. Combustion air; from this point passes through .the grate into thefire and sustains. combustion. v i

The air or gases which are being heated enter the device through the duct 29 and pass overand around the outsideof fiues '16. The flow of the circulating airor gases to be heated is shown by the dot and dash arrows on the. drawings.

These circulating gases then .turn downward in'the general direction shown in Figures 2 and 4,

passing under baffie 30 over bafiie 31 and over arch 32.1 vArch 32 separates the combustion chamber from .the circulating gasesfland may to advantage. be constructed ofsilicon carbide brick or other material which. is adapted to withstand high temperatures and conduct heat readily. r a y The circulating-gases being heated, leave the heater. through exit duct 33 passing over ther mocouple 34 and entering the dryer device-35. From the dryer the circulating gases enter circulating fan 36 through intake 37 and pass through discharge 38 into the intake flue 29; An exhaust stack 39 provided with damper 40' may be connected in' the circuit at any desiredpoint' in order to provide for discarding a desired amount of the circulating gases.

Combustion air blower. 25 is provided with a hand regulated damper 41 and a mechanically operated damper 42 which may be to advantage controlledby thermostat 34. i j

It will be noted that the combustion chamber 4 and the bed of hot fuel 8 serve as sources of radiant heat for maintaining the temperature of arch 32. Large amounts of heat are radiated from the stationary fuel bed. It will be noted that a mass of incandescent fuel weighing in some cases many hundred of pounds, as well as heavy masonrywalls and a heavy carborundum arch, will radiate their heat for a considerable period. Such a condition is not susceptible to quick and accurate response to control equipment owing to the large amount of heat delivered by radiation and stored in this portion of the structure. I

On the other hand, the products of combustion which leave the fuel bed and travel upward and through the metallic fiues 16 can readily be a varied in volume and temperature and will give almost instantaneous response to a damper in circuit with combustion air blower 25.

It has hitherto been a diflicult problem to obtain quick, accurate and close control of heaters of this class, owing to the amount of stored heat which has been referred to above. In the device which I have invented, however, I design the equipment in such a manner that a considerable proportion of the total heat is delivered by the part of the equipment-which is sluggish in changing its temperature, and the balance of the heat I supply through the medium of the metallic tubes which are heated principally by the flue gases. It will be apparent, therefore, that with this construction I am able to almost instantaneously control the quantity of heat delivered through the metallic flue portion of the equipment by controlling the amount of combustion air.

Therefore if the fluctuations in heat demand do not exceed the proportion of total heat supplied by the elements responsive to the damper in the combustion air blower, I have a means whereby I can utilize the radiant heat from the sluggish portions of the heater and the convected heat carried by the flue gases to the metallic heat interchanger.

It will be evident, therefore, that I have developed a device which is rugged, efficient and practical and yet permits of extremely accurate control which is now required in most manufacturing processes.

It will further be obvious that by opening damper 18 in stack 17 or by controlling said damper l8 automatically, I can maintain a hot fire on grate 8 in combustion chamber 4 and, therefore, heat arch 32 to a high temperature without supplying appreciable amounts of heat to flue members 16. By this device, therefore, I

am able to control the amount of heat delivered I by radiation from grate 8 to arch 32, and there& fore to the circulating gases independently of the amount of heat transferred to the circulating gases by convection, that is to say, by means 16 and, therefore, to the circulating gases being heated. I

' It will be further. evident that in case circulating blower 36 should fail to operate, due to any cause Whatever the circulating gases would cease to fiowthrough the heater. Under these conditions no means are provided for removin roaassi the heat from the fiues 16. Under such conditions the fiues 16 might readily become so highly heated that they would be seriously damaged. If, however, damper 18 in stack 1'7 is opened either with or without closing damper 21 in stack 20, then the products of combustion will pass upward and escape-through stack 17 without passing through flues 16 and these fiues will, therefore, not be damaged; The arch 32 being constructed of refractory heat resisting material such as silicon carbide, special alloys, etc., will not be damaged by the radiant heat from grate 8. It will be apparent that the operation of dampers 18 and 21 may be made mechanical and controlled by the air pressure leaving circulating fan 36 if desired.

From the above discussion it will be apparent that I have invented a heater adapted for the use of many fuels and particularly solid fuels. My heater permits a separation of the radiant heat from the convected heat of combustion and permits of independent control of the amount of radiant heat which is eventually delivered to the circulating gases and the amount of convected heat which is eventually delivered to the circulating gases. My invention therefore, permits accurate and prompt regulation and control and provides many safety features not heretofore available. I I I Bailie 31 is intended to receive radiant heat from arch 32 and transmit it to the circulating gases which come in contact with it. Bailie 30 acts in a similar manner and both baffles 30 and 31 serve to protect tubes 16 from radiant heat from arch 32 and, therefore, from grate 8.

In considering my invention it should be understood that many substitutes are possible and still come within the scope of my invention. While I have shown a mechanical underfed stoker for supplying solid fuel, it will be apparent that the fuel may be delivered by hand firing orchain grates; powdered coal burners or oil or gas burners may be used. In any case the combustion chamber serves as a source of radiant heat under the conditions here described. I While I have shown fans for, moving the air it is obvious that any form of compressors, blowers or pumps may be employed. The dampers used may be sliding, rotating or other types. The stacks may be obviously modified in shape, size and location without departing from the spirit of'this invention.

While I have shown a series of tubes as a means of transferring the heat from convection gases, it will be evident that I may replace these tubes with cast metal fiues or I may use special alloys either in part or in whole.

' I prefer to introduce the gases being heated in such a manner that they will first pass over the fiues 16 and second come in contact with the radiant members 32, 31 and 30. In'order to assist in delivering heat from the radiant members I may add baffles or projections as shown by 45, thus creating eddies and more effectively heating the circulating gases.

Obviously flue members 16 may be made vertical or horizontal or inclined and their respective' position with relation to the combustion chamber may be materially changed without departing from the spirit of this invention.

Having now fully described my invention, what I claim as new and wish to secure by Letters Patent in the United States, is as follows:

1. An apparatus for heating fluids, consisting of a fuel chamber having a wall which is heated primarily by radiation from said fluid-containing chamber, another wall heated by convection by gases from said fuel chamber and a temperature control device arranged to vary the heat delivered to the convection heated wall, said control device having a heat sensitive member actuated by the temperature of the fluids being heated, so as to hold the temperature of the fluids bein heated at a predetermined value.

2. A device for heating fluids consisting of a fluid containing chamber, a combustion chamber, a fuel feeding device, a wall of said fluid containing chamber heated primarily by radiation, another wall of said fluid containing chamber heated primarily by convection, and a temperature control device for said gases being heated, acting primarily on the heat delivered to said wall of said fluid containing chamber, which is heated primarily by convection.

3. A device for heating fluids consisting of a fluid containing chamber, a combustion chamber, a fuel feeding device, a surface of said fluid containing chamber heated primarily by radiation, another surface of said fluid containing chamber heated primarily by convection, and a temperature control device for said fluids being heated, acting primarily on the heat delivered to said convection receiving surface, the actuating element of said control device being located in said circulating fluids.

4. A device for heating fluids consisting ofa housing,a combustion chamber therein, a device for burning solid fuel located within said combustion chamber, a'wall separating said combustion chamber from a fluid chamber and arranged to receive heat by radiation from said combustion chamber and a series of flues located in said fluid chamber and communicating with said combustion chamber, said flues serving to impart heat to the circulating fluids, and means for controlling heat flow through said flues.

WILLIAM A. DARRAH. 

